The implementation idea of the window interface is quite simple. The graphics engine is executed by a separate operating system process (it runs in fact a modified wish). Any communication with the graphics engine is done via strings. The interface maps tickles and tickle messages to strings (this is done in a fairly efficient way). In the reverse direction, strings can be mapped back to Oz data types like integers, atoms, lists of integers or lists of atoms.

To get an impression of the efficiency of the implementation, try some examples, as well as the demos and the tools that come with Mozart. They are all built on top of the Tk window programming interface.